Cadmium Ratio Method Research Articles

Standardization and validation of k0-based Neutron Activation Analysis using Apsara-U reactor and its application to pure iron metal and coal sample for trace element determination

The k0-NAA method has been standardized by characterizing the G4 irradiation position of the upgraded Apsara (Apsara-U) reactor. The sub-cadmium to epithermal neutron flux ratio (f) and epithermal neutron flux shape factor (α) were determined taking dual (197Au and 94Zr), triple (197Au, 94Zr and 96Zr) and multi (197Au, 59Co, 64Zn, 68Zn, 96Zr and 94Zr) flux monitors using Cadmium ratio method. The value of f was found to be 19.94 ± 1.02 with average value of α as −0.027 ±0.004. The method was validated by analysing SMELS-II (synthetic multielemental standards) and geological certified reference material (Andesite, AGV-1), wherein results are in good agreement with certified or recommended values. The k0-based NAA method was applied for chemical characterization of pure Iron metal and coal samples. The results obtained were further compared with ICP-OES analysis and the values are found to be in good agreement (t<tcritical) for all the elements determined. F-test was also performed in order to show the reliability of the results in terms of standard deviations.

Neutron capture cross section of Mn53 from irradiation with cold and reactor neutrons

The neutron capture cross section of $^{53}\mathrm{Mn}$ was measured with cold and reactor neutrons by the activation method, relative to the well-known cross section of $^{59}\mathrm{Co}$. Three targets containing a total of $\ensuremath{\approx}{10}^{18}$ atoms $^{53}\mathrm{Mn}$ in the form of chloride salt were prepared using a stock solution obtained from activated accelerator waste in the course of the ERAWAST initiative at Paul Scherrer Institute, Switzerland (PSI). Natural cobalt salt was added to the sample material as an internal neutron flux monitor. The total numbers of $^{53}\mathrm{Mn}$ and $^{59}\mathrm{Co}$ atoms in the target were deduced via mass spectrometric measurements at PSI. Cold-neutron activation was carried out at the ICON beamline at PSI. Reactor activation was performed at the LVR-15 research reactor of Research Centre \ifmmode \check{R}\else \v{R}\fi{}e\ifmmode \check{z}\else \v{z}\fi{} in a well-moderated neutron field of an outer reactor channel. The thermal-neutron capture cross section and the resonance integral were determined by the cadmium ratio method. The induced activities of $^{54}\mathrm{Mn}$ and $^{60}\mathrm{Co}$ were quantified by high-resolution $\ensuremath{\gamma}$-ray spectrometry. The obtained thermal-neutron capture cross section of $76.5\ifmmode\pm\else\textpm\fi{}1.4\phantom{\rule{0.222222em}{0ex}}\mathrm{b}$ agrees well with previously reported results. The uncertainty of this value could be reduced by almost an order of magnitude with respect to older measurements and is on a level comparable to stable nuclides. The resonance integral of $43.1\ifmmode\pm\else\textpm\fi{}1.2\phantom{\rule{0.222222em}{0ex}}\mathrm{b}$ was obtained for the real reactor spectrum with epithermal-spectrum shape factor $\ensuremath{\alpha}=0.025$.

Determination of effective resonance energies for the185Re(n,)186Re and187Re(n,)188Re reactions by cadmium ratio method

The effective resonance energy ($\bar{E}_{r})$ values for the $^{185}$Re(n,$\gamma )^{186}$Re and $^{187}$Re(n,$\gamma )^{188}$Re reactions were measured by using the cadmium ratio method. $^{197}$Au and $^{98}$Mo isotopes were selected as dual monitors to determine the epithermal neutron spectrum shape factor in the irradiation sites of a 37 GBq $^{241}$Am-Be neutron source. The analytical grade rhenium(VII) oxide samples were diluted with Al$_{2}$O$_{3}$ powder to reduce neutron self-shielding effects, and they were put into 1-mm thick small cylindrical polytetrafluoroethylene (PTFE) boxes. Samples were irradiated in a $^{241}$Am-Be neutron source. The activation produced in the irradiated samples was measured in close-counting geometry on the end cap of a Ge detector in order to obtain better counting statistics. The correction factors for gamma-ray self-absorption ($F_{s})$, thermal neutron self-shielding ($G_{th})$, and epithermal neutron self-shielding ($G_{epi})$ effects were determined with suitable approaches. Consequently, the experimental $\bar{E}_{r}$-values were measured to be 3.49 ± 0.54 eV for $^{185}$Re and 41.77 ± 6.79 eV for $^{187}$Re target nuclide, respectively. Furthermore, the $\bar{E}_{r}$-values were theoretically computed through up-to-date resonance data obtained from the ENDF/B VII library using two different approaches. Since there is no experimental data available in the literature for the $\bar{E}_{r}$-values of these isotopes, the results were compared with the theoretical values in the literature.

Measurements of the thermal neutron cross-section and resonance integral for the 108 Pd(n,γ) 109 Pd reaction

Abstract The thermal neutron capture cross-section (σ0) and resonance integral (I0) of the 108Pd(n,γ)109Pd reaction have been measured relative to that of the monitor reaction 197Au(n,γ)198Au. The measurements were carried out using the neutron activation with the cadmium ratio method. Both the samples and monitors were irradiated with and without cadmium cover of 0.5 mm thickness. The induced activities of the reaction products were measured with a well calibrated HPGe γ-ray detector. In order to improve the accuracy of the results, the necessary corrections for the counting losses were made. The thermal neutron capture cross-section and resonance integral of the 108Pd(n,γ)109Pd reaction were determined to be σ0,Pd = 8.68 ± 0.41 barn and I0,Pd = 245.6 ± 24.8 barn, respectively. The obtained results are compared with literature values and discussed.

Determination of effective resonance energy for the 193Ir(n,γ)194Ir reaction by the cadmium ratio method

In this work, the effective resonance energy, E¯r-value for the 193Ir(n,γ)194Ir reaction was measured using cadmium ratio method. A dual monitor (197Au–98Mo), which has convenient resonance properties, was employed for characterization of the irradiation sites. Then analytical grade iridium oxide samples diluted with CaCO3 to lower neutron self-shielding effect stacked in small cylindrical Teflon boxes were irradiated once with a 1mm thick Cd cylindrical box placed in a thermalized neutron field of an 241Am–Be neutron source then without it. The activities produced in samples during 193Ir(n,γ)194Ir reaction were measured using a p-type HPGe detector γ-ray spectrometer with a 44.8% relative efficiency. The correction factors for thermal, epithermal neutron self-shielding (Gth, Gepi), true coincidence summing (Fcoi) and gamma-ray self-absorption (Fs) effects were determined with appropriate approaches and programs. Thus, the experimental E¯r-value was determined to be 2.65±0.61eV for 193Ir target nuclide. The recent data for Q0 and FCd values for E¯r determination were based on k0-NAA online database. The present experimental E¯r value was calculated and compared with more recent values for Q0 and FCd for 193Ir. Additionally, the E¯r-values was theoretically calculated from the up-to-date resonance data obtained from ENDF/B VII library using two different approaches. Since there is no experimentally determined E¯r-value for the 193Ir isotope, the results are compared with the calculated ones given in the literature.

Characterization of Irradiation Sites of Apsara Reactor for $k_{0}$-Based IM-NAA and Its Validation and Application

Three irradiation positions of Apsara reactor were characterized by determining epithermal neutron spectrum shape factor <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(\alpha)$</tex></formula> and sub-cadmium to epithermal neutron flux ratio <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(f)$</tex> </formula> for <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm k}_{0}$</tex> </formula> -based Internal Monostandard Neutron Activation Analysis (IM-NAA). The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\alpha$</tex></formula> values were determined by cadmium ratio method using six neutron flux monitors (In, Au, Co, Mo, Zn and Zr). The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f$</tex> </formula> -value was also determined by cadmium ratio method using an Au monitor. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\alpha$</tex></formula> values of two irradiation positions are found to be positive, which indicated softened epithermal neutron spectra whereas <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\alpha$</tex> </formula> value of the third one is negative indicating hardened neutron spectrum. IAEA reference material, RM SL-1 (Lake Sediment) was analyzed by IM-NAA using experimentally determined <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f$</tex></formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\alpha$</tex></formula> values of all three irradiation positions. A total of 16 elemental concentrations were determined using Sc as the internal monostandard and the values are found to be in good agreement with respect to the certified or information values. As an application of IM-NAA, two ceramic archaeological samples along with one soil sample were analyzed using Sc as the monostandard.

Characterization of low power research reactor neutrons for the validation of k0-INAA standardization based on k0-IAEA software

Channel Bsite2 of Ghana research reactor-1 has been characterized for k0-INAA application. Cadmium ratio and bare multi-monitor were used to determine flux parameters using 0.1%Au–Al, Fe, and Zr wire as flux monitors. The parameters determined were 18.36±1.91, 0.0479±0.012, 5.12×1011±0.42×1011ncm−2s−1, 2.74×1010±0.14×1010ncm−2s−1, 7.73×1010±0.16×1010ncm−2s−1 and 16.75±1.58, −0.034±0.0028, 4.28×1011±1.71×1011ncm−2s−1, 2.55×1010±0.15×1010ncm−2s−1 respectively for thermal-to-epithermal flux ratio, alpha, thermal neutron, epithermal neutron and fast neutron flux using cadmium ratio and multi-monitor method accordingly. The k0-INAA performance assessment based on z-score distributions showed most results within |z|<2.

Determination of the f parameter for k 0-neutron activation analysis at the Australian 20 MW OPAL research reactor

In the k 0 method of standardisation in neutron activation analysis (k 0-NAA), the ratio of thermal to epithermal neutrons, a value known as f, is fundamental in accurately determining the concentration of elements within the sample. Research into determining this f value via the cadmium ratio method was undertaken for two positions within the 20 MW Open Pool Australian Light water (OPAL) research reactor (Lucas Heights, NSW, Australia). A short irradiation and long irradiation position were assessed via two methods; the conventional cadmium ratio method based on the Hogdahl formalism, with f values of 2,666 ± 255 and 1,538 ± 258 being calculated respectively for the short and long positions, and an ASTM-INVAP-based cadmium ratio method, which allows for the higher neutron temperature of OPAL to be accounted for, with f values of 3,057 ± 318 and 1,755 ± 312 being calculated respectively. These values were validated by analysis of NIST standard reference materials (SRM™), with good agreement between experimental values and reference and literature values being observed, showing the accuracy and suitability of these values for OPAL. Additionally, the high values of f shown endorse the strength of performing k 0-NAA at OPAL. This manuscript publishes the first values of f from OPAL and provides a detailed description of the method employed.

Erratum to: Determination of k 0-values for some elements in neutron capture gamma-ray for prompt gamma activation analysis

Exploration and modification of data for k 0-PGAA (prompt γ-ray activation analysis) values used as standards for k 0 standardization are needed. An integrated system has been installed and calibrated in Hot Laboratories Center for PGAA, using 252Cf isotopic neutron source with neutron flux of 6.16E8 n/cm2 s. The prompt k 0-factors of about 12 elements were determined versus the 1951.1 keV γ-ray of the 35Cl, as well as analyzing crude oil and oil product samples. The concentrations of the elements in crude oil H, B, Mg, Al, Na, Si, P, S, Cl, V and Cd were 1.18E5, 0.084, 5.48E2, 8.45E2 4.88E2, 1.62E2, 3.72E2, 8.2, 144.3, 393 and 209.2 ppm while in oil product samples were 1.32E5, 5.87, 4.56E2, 4.22E2, 7.16E3, 699, 157, 8.74, 492.3, 61 and 198.2 ppm. Validation of the k 0-PGAA was applied in analyzing standard IAEA reference material (soil-7) which give good agreement with the literature data. The 252Cf neutron beam in radiation position was characterized by the cadmium-ratio method, and found that the cadmium ratio (f), was 160.

Experimental determination of effective resonance energies for 158Gd(n,γ) 159Gd and 179Hf(n,γ) 180mHf reactions

The accuracy and precision of effective resonance energy E ¯ r parameter is an important point in the determination of the mass fraction of an analyte contained in the sample when NAA is used. Because the effective resonance energy E ¯ r is an essential parameter, which is directly introduced in the k 0–NAA standardization method. Therefore, the effective resonance energies E ¯ r for the 158Gd(n,γ) 159Gd and 179Hf(n,γ) 180mHf reactions were determined by cadmium ratio method using 55Mn and 98Mo monitors. The samples were irradiated in an isotropic neutron field of 241Am–Be neutron sources. The induced activities for the radioisotopes were produced in the samples with and without a 1 mm-thick Cd shield and then measured with a p-type high pure Ge detector. The correction factors required for thermal neutron self-shielding ( G th ) and resonance neutron self-shielding ( G epi ) for the irradiated samples, and self absorption ( F s ) and true coincidence summing ( F coi ) effects for the measured γ-rays were taken into account. The experimental E ¯ r -values are found to be 49.6 ± 10.4 eV for 158Gd and 17.0 ± 3.5 eV for 179Hf target isotopes, respectively. The E ¯ r -values of 158Gd and 179Hf were also theoretically calculated by using the recent resonance data in the literature. Since the experimentally determined E ¯ r -values for the 158Gd(n,γ) 159Gd and 179Hf(n,γ) 180mHf reactions are not available in literature, the present experimental results for the E ¯ r energies are thus compared with the present and earlier theoretical values, respectively. The presently measured E ¯ r value for 158Gd is generally larger than those obtained E ¯ r values from theoretical approaches by ∼9.1–16.9%. Whereas, the theoretically calculated E ¯ r -values for 179Hf isotope deviated substantially from the presently measured value by ∼16.9–37.6%. The reasons for this discrepancy are discussed in this paper.

Determination of k 0-factors and validation of k 0-INAA for short-lived nuclides

For standardization of k 0-based instrumental neutron activation analysis, k 0-factors for short-lived nuclides (half-lives—11 s to 37 min) of elements F, Se, Sc, Al, V, Ti, Cu, Ca, Mg, I, and Cl with respect to gold (197Au) were determined using pneumatic carrier facility (PCF) at CIRUS reactor of BARC, Mumbai. Characterization of PCF was carried out by cadmium-ratio method using Au and Zr. The experimental k 0-factors of the isotopes were found to be in good agreement with the recommended k 0-factors in most of the cases, as evident from the values of % error and U-score at 95% confidence level. The method was validated by determining concentrations of elements through their short-lived nuclides in one type of the synthetic multielement standards (SMELS-I) obtained from SCK-CEN, Belgium. The method was also applied for determination of concentrations of some of the elements in two reference materials of IAEA, SL-3, and SL-1.

Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,γ)175Yb reaction by the cadmium ratio method

The thermal-neutron cross-section and the resonance integral for the 174Yb(n,γ)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am–Be neutron sources. The gamma-ray spectra from the activated samples were measured with a calibrated n-type high-purity Ge detector. The experimental results were corrected for the correction factors calculated for thermal and epithermal neutron self-shielding effects, epithermal neutron spectrum shape and gamma-ray self attenuation. Thus, the thermal neutron cross-section for the 174Yb(n,γ)175Yb reaction is found to be 126.5±6.6b, relative to that of the 55Mn monitor. The resonance integral value for the 174Yb(n,γ)175Yb reaction is found to be 59.6±8.5b, at cadmium cut-off energy of a 0.55eV. Using the measured cadmium ratios of 55Mn and 174Yb, the result for resonance integral of the 174Yb(n,γ)175Yb reaction has also been obtained relative to the reference value of the 55Mn monitor. The present results for the 174Yb(n,γ)175Yb reaction agree well only with the recent experimental ones obtained by Kafala et al. [1] and De Corte and Simonits [2] within uncertainty limits. However, the previously reported experimental data for the thermal neutron cross-section for this reaction are distributed between 24 and 141b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30–69b.

Experimental determination of effective resonance energies for the (n,γ) reactions of 71Ga, 75As, 164Dy, 170Er by the cadmium ratio method

The effective resonance energy E ¯ r -values for the (n, γ) reactions of 71Ga, 75As, 164Dy, 170Er were determined by the cadmium ratio method using dual monitor ( 55Mn– 98Mo) having favorable resonance properties. The powder samples with and without a 1 mm thick Cd cylindrical box were irradiated in an isotropic neutron field obtained from three 241Am–Be neutron sources. The induced activities were measured with a 120.8% relative efficient p-type Ge detector. The necessary correction factors for thermal neutron self-shielding ( G th) and resonance neutron self-shielding ( G epi) effects were taken into account. Thus, the experimentally determined E ¯ r -values were 174 ± 36 eV for 71Ga, 112 ± 23 eV for 75As, 225 ± 47 eV for 164Dy and 129 ± 27 eV for 170Er, respectively. The present experimental results for the E ¯ r -values were also theoretically calculated from the newest resonance data. Since the experimentally determined E ¯ r -values for the 71Ga, 75As, 164Dy and 170Er isotopes are not available in literature, the present experimental results are compared only with the present and earlier calculated ones. It is found that there are still large discrepancies (within range of 3–15%) between the experimentally determined E ¯ r -values and the calculated ones obtained by recent resonance data for the above isotopes. A wide variation of the available E ¯ r -values implies the need for the new experimental determinations of E ¯ r -values for other isotopes, especially used in k 0 standardization studies.

Evaluation of imaging plate technique coupled with activation detector as the passive neutron monitor

The spatial distribution of neutrons was measured at the muon science laboratory of KEK by the activation detector method using an imaging plate for the radioactivity measurement. It was confirmed that this method is highly sensitive to detect the average neutron dose of 10 µSv/h. The distribution of thermal and epithermal neutrons was also measured in the experimental room. The cadmium ratio inside the experimental room is one except for the neutron leakage point. The spatial distribution of neutrons inside the concrete shield of KENS was measured by the same method. Aluminum and gold foils were used for the measurement of fast and thermal neutrons, respectively. Two dimensional change of the reaction rate of the 27Al(n,α)24Na reaction shows a good agreement with the results calculated by the Monte Carlo simulation using MARS14 code. Thermal and epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method. The flux ratios were about 30 and almost constant for every slot except for the surface of the shield, because the cadmium ratio is 2. This method was very useful to measure the activity of many pieces of detector simultaneously without any efficiency and decay correction. Wide dynamic range and high sensitivity are also the merit of this method.

KENS Shielding Experiment (2): Measurement of the Neutron Spatial Distribution inside and outside of a Concrete Shield using an Activation Foil and an Imaging Plate Technique

The spatial distribution of neutrons inside and outside the concrete shield of KENS was measured by the combined use of activation detectors and an imaging plate. Aluminium and gold foils were used for neutron flux measurements of both high-energy and thermal neutrons, respectively. The obtained results concerning attenuation of the high-energy neutron flux show a good agreement with results obtained by a Monte Carlo simulation using the MARS 14 code. The thermal and epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method, and gave about 30, which almost constant inside the concrete shield. It is concluded that the method, which combined the use of activation detectors and an imaging plate, was very useful to measure the activity of many pieces of the detector simultaneously without any efficiency or decay correction. A wide dynamic range and a high sensitivity are also merits of this method.

An alternative method for the measurement of thermal neutron flux (modified cadmium ratio method)

An alternative method of approach has been developed for the measurement of thermal neutron flux. The method depends only on the activity of the bare foil if the cadmium ratio at the irradiation position is known. The method has been tested on the GHARR-1 facility at the Ghana Atomic Energy Commission using gold and indium foils for the measurement of the thermal neutron flux in the flux range of 1010–1012 n·cm−2·s−1 and the results compare very well with those obtained using the conventional method (cadmium separation method).

CROSS SECTIONS AND RESONANCE INTEGRALS FOR THE NEUTRON ACTIVATION OF 103Rh

The cadmium ratio method has been used to determine the ratio I′/σ0 for activation of 103Rh, where I′ is the reduced resonance integral and σ0 is the 2 200-m/s cross section. For the production of 104gRh we obtain I′/σ0 = 8.1 ± 0.3 and, for 104mRh, I′/σ0 = 7.4 ± 0.3. These results disagree with a value of ~3.5 obtained in an earlier cadmium ratio measurement. We have also measured the half-lives of the two isomers. In the following table, which summarizes our results, the thermal cross sections are normalized to an absorption cross section in 103Rh of 146 barns and a value of 12.2 for the production of 104gRh relative to 104mRh per 103Rh capture.[Formula: see text]The total reduced resonance integral is 1 175 barns for activation compared with a value of 1 015 ± 25 barns for absorption derived from published resonance parameters.

The Resonance Fission Integrals of U235, Pu239, and Pu241

The resonance fission integrals of U235, Pu239, and Pu241 have been measured relative to the gold resonance capture integral by the cadmium ratio method. The cadmium ratios were measured in a react...